1. Field of the Invention
The present invention relates to novel block polymers comprising polyether blocks and oligamide blocks, designated block copolyetheramides.
2. Description of the Prior Art
Numerous block copolyetheramides are known to this art.
Copolyetheramides having the formula ##STR3## in which A is a polyamide block and B an aliphatic polyether block, are described in French Patents Nos. 2,273,021 and 2,401,947 assigned to the assignee hereof.
These are prepared by molten state reaction of a dicarboxylic polyamide having an Mn ranging from 300 to 15,000 with a polyetherdiol having an Mn ranging from to 6,000 under a high vacuum at temperatures ranging from 100.degree. to 400.degree. C. in the presence of one or more metal tetraalkoxides of formula M(OR).sub.4 as catalyst, wherein M is titanium, hafnium or zirconium and R is a hydrocarbon radical having from 1 to 24 carbon atoms.
These block copolyetheramides have good mechanical and chemical properties.
In French Patent No. 2,384,810 copolyetheresteramides are described which are prepared by polymerization, under autogenous pressure at temperatures ranging from 230.degree. to 300.degree. C., of a mixture of one or more polyamide monomers, an alpha,omega-dihydroxy(polytetrahydrofuran) (or PTMG) having an Mn ranging from 160 to 3,000, and at least one diacid, in the presence of water, the water then being removed from the reaction mixture, which is then returned to normal or reduced pressure at a temperature ranging from 250.degree. to 280.degree. C.
The polymers obtained are also sequenced or block polymers and have good low-temperature impact strength.
However, the polymers prepared according to the above patents have, for a given hardness, a lower melting point than those according to the invention.
U.S. Pat. No. 4,307,227 describes adhesives of the hot-melt type comprising 50% to 80% of recurring structural units derived from caprolactam and mixtures of dicarboxylic acids, primary amines and polyoxyalkylene glycol.
The process employed (reaction of all of the constituents without catalyst at a temperature ranging from 220.degree. to 250.degree. C.) does not permit the synthesis of polymers in which the polyether blocks have an Mn higher than 1,000.
Patent Applications J-63/035,622 and J-63/277,239 relate to block copolyetheramides prepared by reacting an oligamide of PA-6,6 containing one or more polyoxyalkylenedioxy blocks with a polyoxyalkylene glycol or a diol of low molecular weight under a high vacuum at a temperature higher than 250.degree. C. in the presence of an esterification catalyst, which is a metal tetraalkoxide.
The use of polyoxyalkylene glycol or diol of low molecular weight results in polymers which have melting points distinctly lower than those of the present invention.
Patent Application J-63/182,343 relates to block copolyetheramides prepared by molten state reaction of PA-6,6 blocks having diamine endgroups with polyether blocks having dicarboxylic chain endgroups. The polymers obtained according to this application have a high melting point, higher than 230.degree. C., which necessitates high conversion temperatures and, therefore, risks of degradation of the polymers during their conversion.